Such medical supporting implants are used primarily for treatment of stenoses in coronary vessels, but may also be used for other indications in other types of vessels in the body. As a rule, such supporting implants have a tubular base body comprising flexible struts formed from the base body by laser cutting. A wide variety of designs are known for the strut structure. The starting point for the present disclosure is stent designs with meandering peripheral supporting struts such that, at node points of at least two struts, the struts form an acute angle with one another. On dilatation of the implant, this acute angle increases under bending stress on the struts at the node. One problem with such stents is that during crimping the stent is compressed into the state for inserting the stent into the respective vessel on a balloon catheter, and a great plastic deformation then occurs which has a significant influence on the elastic recoil of the stent structure. The goal is for the recoil effect to be minimized. This can be ensured to a limited extent by local plastic deformation of the stent structure, e.g., in the area of the node points between neighboring struts of the peripheral supporting webs. However, due to the material, there are limits to the plastic deformation. When these limits are exceeded, there is the risk of a structural failure, e.g., on reaching the elongation at break in the material.
Due to the restriction that material-specific limit values must not be exceeded, it is problematical accordingly to achieve good recoil performance with the stent. Enlarging the cross section of the struts of the stent structure is also possible only to a limited extent.
To solve the above problems, approaches for making stent structures expandable through mechanical constructions without plastic deformation are already known. U.S. Pat. No. 5,824,054 discloses a vascular supporting implant comprising a polytetrafluoroethylene (“PTFE”) film sheet with peripheral rows of perforations coiled onto itself. Projections integrally molded on the foam sheet may mesh with the perforations, these projections being aligned so that compression of the stent is prevented.
U.S. Pat. No. 5,441,515 discloses a “ratchet stent,” as it is referred to therein, in which the cylindrical stent structure is formed by tongues running circumferentially. These tongues are held together by a common connecting crosspiece, a slot for engagement of the end of the tongue being arranged in each crosspiece. On their lateral edges, the tongues are provided with rows of locking teeth which act unidirectionally. The tongue ends are inserted far into the slots in the compressed position. When the stent is dilated, the tongues gradually expand outward out of the slots preventing contraction by the locking teeth engaging with the slot ends.
Finally, U.S. Patent Publication No. 2007/0061004 discloses an expanded stent in which mesh structures running in the circumferential direction are subdivided into individual sections which allow widening of the stent structure by displacement of the individual elements toward one another. The mesh structures with strap-like protrusions engage in corresponding openings in the neighboring mesh structure.